English

Noun

Translations

Pain, in the sense of physical pain, is a typical
sensory experience that may be described as the unpleasant
awareness of a noxious stimulus or bodily harm. Individuals get
acquainted to pain through various daily hurts and aches, and
occasionally through more serious injuries or illnesses. For
scientific and clinical purposes, pain is defined by the
International Association for the Study of Pain (IASP) as "an
unpleasant sensory and emotional experience associated with actual
or potential tissue damage, or described in terms of such
damage".

Pain is highly subjective to the individual
experiencing it. A definition that is widely used in nursing was
first given as early as 1968 by Margo
McCaffery: "'Pain is whatever the experiencing person says it
is, existing whenever he says it does".

Pain of any type is the most frequent reason for
physician consultation in the United States, prompting half of all
Americans to seek medical care annually. It is a major symptom in
many medical conditions, significantly interfering with a person's
quality of life and general functioning. Diagnosis is based on
characterizing pain in various ways, according to duration,
intensity, type (dull, burning or stabbing), source, or location in
body. Usually pain stops without treatment or responds to simple
measures such as resting or taking an analgesic, and it is then
called ‘acute’
pain. But it may also become intractable and develop into a
condition called chronic
pain, in which pain is no longer considered a symptom but an
illness by itself. The study of pain has in recent years attracted
many different fields such as pharmacology, neurobiology, nursing
sciences, dentistry, physiotherapy, and psychology. Pain
medicine is a separate subspecialty figuring under some medical
specialties like anesthesiology, physiatry, neurology,
psychiatry.

Pain is part of the body's defense system,
triggering a reflex reaction to retract from a painful stimulus,
and helps adjust behaviour to increase avoidance of that particular
harmful situation in the future. Given its significance, physical
pain is also linked to various cultural, religious, philosophical,
or social issues.

Clarification on the use of certain pain-related terms

The word pain used without a modifier usually refers to
physical pain, but it may also refer to pain in the broad sense,
i.e. suffering. The
latter includes physical pain and mental pain, or any unpleasant
feeling, sensation, and emotion. It may be described as a private
feeling of unpleasantness and aversion associated with harm or
threat of harm in an individual. Care should be taken to make the
appropriate distinction when required between the two meanings. For
instance, philosophy
of pain is essentially about physical pain, while a
philosophical outlook on pain is rather about pain in the broad
sense. Or, as another quite different instance, nausea or itch are not 'physical pains', but
they are unpleasant sensory or bodily experience, and a person
'suffering' from severe or prolonged nausea or itch may be said 'in
pain'.

Nociception,
the unconscious activity induced by a harmful stimulus in sense
receptors, peripheral nerves, spinal column and brain, should not
be confused with physical pain, which is a conscious
experience.

Qualifiers, such as mental, emotional, psychological, and
spiritual, are often used for referring to more specific types of
pain or suffering. In particular, 'mental pain' may be used in
relationship with 'physical pain' for distinguishing between two
wide categories of pain. A first caveat concerning such a
distinction is that it uses 'physical pain' in a sense that
normally includes not only the 'typical sensory experience' of
'physical pain' but also other unpleasant bodily experience such as
itch or nausea. A second caveat is that the terms physical or
mental should not be taken too literally: physical pain, as a
matter of fact, happens through conscious minds and involves
emotional aspects, while mental pain happens through physical
brains and, being an emotion, it involves important bodily
physiological aspects.

The term unpleasant or unpleasantness commonly means painful or
painfulness in a broad sense. It is also used in (physical) pain
science for referring to the affective dimension of pain, usually
in contrast with the sensory dimension. For instance:
“Pain-unpleasantness is often, though not always, closely linked to
both the intensity and unique qualities of the painful sensation.”
Pain science acknowledges, in a puzzling challenge to IASP
definition, that pain may be experienced as a sensation devoid of
any unpleasantness: see below pain
asymbolia. Neuropathic pain may refer to
peripheral neuropathic pain, which is caused by damage to
nerves, or to central
pain, which is caused by damage to the brain, brainstem, or
spinal cord.

Nociceptive pain and neuropathic pain are the two
main kinds of pain when the primary mechanism of production is
considered. A third kind may be mentioned: see below the rare case
of psychogenic
pain.

Nociceptive pain may be classified further in
three types that have distinct organic origins and felt
qualities.

Superficial somatic
pain (or cutaneous
pain) is caused by injury to the skin or superficial tissues.
Cutaneous nociceptors terminate just below the skin, and due to the
high concentration of nerve endings, produce a sharp, well-defined,
localized pain of short duration. Examples of injuries that produce
cutaneous pain include minor wounds, and minor (first degree)
burns.

Visceral pain
originates from body's viscera, or organs. Visceral nociceptors are
located within body organs and internal cavities. The even greater
scarcity of nociceptors in these areas produces pain that is
usually more aching or cramping and of a longer duration than
somatic pain. Visceral pain may be well-localized, but often it is
extremely difficult to localize, and several injuries to visceral
tissue exhibit "referred" pain, where the sensation is localized to
an area completely unrelated to the site of injury.

Nociception is the unconscious afferent activity
produced in the peripheral and central nervous system by stimuli
that have the potential to damage tissue. It should not be confused
with pain, which is a conscious experience.

The
gate control theory of pain describes how the perception of
pain is not a direct result of activation of nociceptors, but
instead is modulated by interaction between different neurons, both
pain-transmitting and non-pain-transmitting. In other words, the
theory asserts that activation, at the spine level or even by
higher cognitive brain processes, of nerves or neurons that do not
transmit pain signals can interfere with signals from pain fibers
and inhibit or modulate an individual's experience of pain.

Pain may be experienced differently depending on
genotype; as an example
individuals with red hair may be more susceptible to pain caused by
heat, but redheads with a non-functional melanocortin
1 receptor (MC1R) gene are less sensitive to pain from electric
shock. Gene Nav1.7 has been
identified as a major factor in the development of the
pain-perception systems within the body. A rare genetic mutation in
this area causes non-functional development of certain sodium
channels in the nervous system, which prevents the brain from
receiving messages of physical damage, resulting in
congenital insensitivity to pain. The same gene also appears to
mediate a form of pain hyper-sensitivity, while other mutations may
be the root of
paroxysmal extreme pain disorder.

Evolutionary and behavioral role

Pain is part of the body's defense system,
triggering mental and physical behavior to end the painful
experience. It promotes learning so that repetition of the painful
situation will be less likely.

Despite its unpleasantness, pain is an important
part of the existence of humans and other animals; in fact, it is
vital to healthy survival (see below Insensitivity
to pain). Pain encourages an organism to disengage from the
noxious stimulus associated with the pain. Preliminary pain can
serve to indicate that an injury is imminent, such as the ache from
a soon-to-be-broken bone. Pain may also promote the healing
process, since most organisms will protect an injured region in
order to avoid further pain.

Interestingly, the brain itself is devoid of
nociceptive tissue, and hence cannot experience pain. Thus, a
headache is not due to
stimulation of pain fibers in the brain itself. Rather, the
membrane surrounding the brain and spinal cord, called the dura mater, is
innervated with pain receptors, and stimulation of these dural
nociceptors is thought to be involved to some extent in producing
headache pain. The vasoconstriction of pain-innervated blood
vessels in the head is another common cause. Some evolutionary biologists have
speculated that this lack of nociceptive tissue in the brain might
be because any injury of sufficient magnitude to cause pain in the
brain has a sufficiently high probability of being fatal that
development of nociceptive tissue therein would have little to no
survival benefit.

Chronic pain, in which the pain becomes
pathological rather than beneficial, may be an exception to the
idea that pain is helpful to survival, although some specialists
believe that psychogenic chronic pain exists as a protective
distraction to keep dangerous repressed emotions such as anger or
rage unconscious. It is not clear what the survival benefit of some
extreme forms of pain (e.g. toothache) might be; and the
intensity of some forms of pain (for example as a result of injury
to fingernails or
toenails) seem to be
out of all proportion to any survival benefits.

Diagnosis

To establish an understanding of an individual's
pain, health-care practitioners will typically try to establish
certain characteristics of the pain:

Quality

Intensity

Localization

Radiation

Frequency and Duration

Onset and Offset

Exacerbating Factors

Ameliorating Factors

By using the gestalt of these characteristics,
the source or cause of the pain can often be established. A
complete diagnosis of pain will require also to look at the
patient's general condition, symptoms, and history of illness or
surgery. The physician may order blood tests, X-rays, scans, EMG,
etc. Pain clinics may investigate the person's psychosocial history
and situation.

Pain assessment also uses the concepts of
pain
threshold, the least experience of pain which a subject can
recognize, and pain
tolerance, the greatest level of pain which a subject is
prepared to tolerate. Among the most frequent technical terms for
referring to abnormal perturbations in pain experience, there are:

allodynia, pain
due to a stimulus which does not normally provoke pain,

hyperalgesia,
an increased response to a stimulus which is normally painful,

hypoalgesia,
diminished pain in response to a normally painful
stimulus.

Verbal characterization

The quality of the pain remains a key
characteristic, and is often the first question a practitioner will
ask. Typical descriptions of pain quality include sharp, stabbing,
tearing, squeezing, cramping, burning, lancinating (electric-shock
like), or heaviness. It may be experienced as throbbing, dull,
nauseating, shooting or a combination of these. Indeed, individuals
who are clearly in extreme distress such as from a myocardial
infarction may not describe the sensation as pain, but instead
as an extreme heaviness on the chest. Another individual with pain
in the same region and with the same intensity may describe the
pain as tearing which would lead the practitioner to consider
aortic dissection. Inflammatory pain is commonly associated with
some degree of itch
sensation, leading to a chronic urge to rub or otherwise stimulate
the affected area. The difference between these diagnoses and many
others rests on the quality of the pain. The McGill
Pain Questionnaire is an instrument often used for verbal
assessment of pain.

Intensity

Pain may range in intensity from slight through
severe to agonizing and can appear as constant or intermittent. The
threshold
of pain varies widely between individuals. Many attempts have been
made to create a pain scale
that can be used to quantify pain, for instance on a numeric scale
that ranges from 1 to 10 points. The purpose of these scales is to
monitor an individual's pain over time, allowing care-givers to see
how a patient responds to therapy for example. Accurate
quantification can also allow researchers to compare results
between groups of patients.

Localization

Pains are usually called according to their
subjective localization in a specific area or region of the body:
headache, toothache, shoulder pain, abdominal pain, back pain,
joint pain, myalgia, etc. Localization is not always accurate in
defining the problematic area, although it will often help narrow
the diagnostic possibilities. Some pain sensations may be diffuse
(radiating) or referred. Radiation of pain occurs in neuralgia when stimulus of a
nerve at one site is perceived as pain in the sensory distribution
of that nerve. Sciatica, for
instance, involves pain running down the back of the buttock, leg
and bottom of foot that results from compression of a nerve root in
the lumbar spine. Referred
pain usually happens when sensory fibres from the viscera enter
the same segment of the spinal cord as somatic nerves i.e. those
from superficial tissues. The sensory nerve from the viscera
stimulates the nearby somatic nerve so that the pain localization
in the brain is confused. A well-known example is when heart damage
is perceived as pain the left shoulder or arm.

Management

Medical management of pain has given rise to a
distinction between acute pain and chronic
pain. Acute pain is 'normal' pain, it is felt when hurting a
toe, breaking a bone, having a toothache, or walking after an
extensive surgical operation. Chronic pain is a 'pain illness', it
is felt day after day, month after month, and seems impossible to
heal.

In general, physicians are more comfortable
treating acute pain, which usually is caused by soft tissue damage,
infection and/or inflammation among other causes. It is usually
treated simultaneously with pharmaceuticals,
commonly analgesics,
or appropriate techniques for removing the cause and for
controlling the pain sensation. The failure to treat acute pain
properly may lead to chronic pain in some cases.

General physicians have only elementary training
in chronic pain
management. Often, patients suffering from it are referred to
various medical specialists. Though usually caused by an injury, an
operation, or an obvious illness, chronic pain may as well have no
apparent cause, or may be caused by a developing illness or
imbalance. This disorder can trigger multiple psychological
problems that confound both patient and health care providers,
leading to various differential diagnoses and to patient's feelings
of helplessness and hopelessness. Multidisciplinary pain clinics
are growing in number since a few decades.

Anesthesia

Anesthesia is
the condition of having the feeling of pain and other sensations
blocked by drugs that induces a lack of awareness. It may be a
total or a minimal lack of awareness throughout the body (i.e.
general anesthesia), or a lack of awareness in a part of the body
(i.e. regional or local anesthesia).

Analgesia

Analgesia is an
alteration of the sense of pain without loss of consciousness. The
body possesses an endogenous analgesia system,
which can be supplemented with painkillers or analgesic drugs to regulate
nociception and
pain. Analgesia may occur in the central nervous system or in
peripheral nerves and nociceptors. The perception of pain can also
be modified by the body according to the
gate control theory of pain.

The endogenous central analgesia system is
mediated by 3 major components : the periaquaductal
grey matter, the nucleus
raphe magnus and the nociception inhibitory neurons within the
dorsal
horns of the spinal cord, which act to inhibit
nociception-transmitting neurons also located in the spinal dorsal
horn. The peripheral regulation consists of several different types
of opioid
receptors that are activated in response to the binding of the
body's endorphins.
These receptors, which exist in a variety of areas in the body,
inhibit firing of neurons that would otherwise be stimulated to do
so by nociceptors.

The
gate control theory of pain postulates that nociception is
"gated" by non-noxious stimuli such as vibration. Thus, rubbing a
bumped knee seems to relieve pain by preventing its transmission to
the brain. Pain is also "gated" by signals that descend from the
brain to the spinal cord to suppress (and in other cases enhance)
incoming nociceptive information.

Hypnosis as well
as diverse perceptional techniques provoking altered states of
consciousness have proven to be of important help in the management
of all types of pain.

Some kinds of physical manipulation or exercise
are showing interesting results as well.

Special cases

Phantom pain

Phantom
limb pain is the sensation of pain from a limb that has been
lost or from which a person no longer receives physical signals. It
is an experience almost universally reported by amputees and quadriplegics. Phantom pain
is a neuropathic pain.

Pain asymbolia

Pain science acknowledges, in a puzzling
challenge to IASP definition,

Insensitivity to pain

The ability to experience pain is
essential for protection from injury, and recognition of the
presence of injury. Insensitivity to pain may occur in special
circumstances, such as for an athlete in the heat of the action, or
for an injured soldier happy to leave the battleground. This
phenomenon is now explained by the gate
control theory. However, insensitivity to pain may also be an
acquired impairment following conditions such as spinal cord
injury, diabetes mellitus, or more rarely Hansen's
Disease. A few people can also suffer from
congenital insensitivity to pain, or congenital analgesia, a
rare genetic defect that puts these individuals at constant risk
from the consequences of unrecognized injury or illness. Children
with this condition suffer carelessly repeated damages to their
tongue, eyes, bones, skin, muscles. They may attain adulthood, but
they have a shortened life expectancy.

Psychogenic pain

Psychogenic
pain, or psychalgia,
is pain which to the sufferer is indistinct from actual physical
pain, but which is caused by a psychological process. It occurs
rarely, and generally in persons with a mental
disorder. Currently, it is considered as physical pain, in
conformity with IASP definition of pain as "an unpleasant sensory
and emotional experience associated with actual or potential tissue
damage, or described in terms of such damage" (emphasis
added).

Philosophy
of pain is a branch of philosophy of mind that deals
essentially with physical pain. Identity theorists assert that the
mental state of pain is completely identical with some physical
state caused by various physiological causes. Functionalists
consider pain to be defined completely by its causal role and
nothing else.

Religious or secular traditions usually define
the nature or meaning of physical pain in every society. Sometimes,
extreme practices are highly regarded:
mortification of the flesh, painful rites of
passage, walking on hot coals, etc.

Variations in pain threshold or in pain tolerance
occur between individuals because of genetics, but also according
to cultural, ethnical, or gender background.

Physical pain is an important political topic in
relation with various issues, including resources distribution for
pain management, drug
control, torture,
pain
compliance (see also pain beam,
pain
maker, pain ray).
Corporal
punishment is the deliberate infliction of pain intended to
punish a person or change a his/her behavior. Historically
speaking, most punishments, whether in judicial, domestic, or
educational settings, were corporal in basis.

More generally, it is rather as a part of pain in
the broad sense, i.e. suffering, that physical pain
is dealt with in cultural, religious, philosophical, or social
issues.

In other species

It is not scientifically possible to prove
whether an animal, or a human for that matter, experiences pain or
not. However, the presence of pain can be inferred through physical
and behavioral reactions. Specialists currently believe that all
vertebrates can feel pain, and that certain invertebrates, like the
octopus, might too. As for other animals, plants, or other
entities, their ability to feel physical pain is presently a
question beyond the scientific reach.

Veterinary medicine uses, for actual or potential
animal pain, the same analgesics and anesthetics as used in
humans.